Pulp screen



Patented May 16, 1933 UNITED STATES PATENT OFFICE JAMES R. DUNBAR, OF ATHOLVILLE, NEW BRUNSWICK, CANADA, ASSIGNOR '10 THOMAS L. DUNBAR, OF MONTREAL, QUEBEC, CANADA PULP SCREEN Application filed July 24, 1931. Serial No. 552,942.

This invention relates in general to machinery for screening paper pulp and relates specifically to the flat type of screens in which the stock is caused to flow over slotted plates through which the acceptable stock passes, the screening effect being augmented by the vibration of diaphragms arranged beneath the plates.

The mechanism at present in general use to effect vibration of the diaphragms comprlses a shaft carrying a plurality of multi-throw cams, one for'each diaphragm, adapted to' engage push rods connected to the diaphragms to lift the diaphragms. A spring is connected to each push rod to urge the rods and diaphragms downwardly. As the number of upward diaphragm movements 1s between 500 and 1000 per minute, the springs must be very heavy in order to overcome, with sufiicient rapidity, the inertia of the parts and the suction effect of downward dia of a rock shaft disposed beneath and longitudinally of the row of diaphragms and having arms projecting from opposite sides.

thereof and flexibly connected severally to push rods which are in turn connected to the diaphragms, and means to rock said shaft whereby the diaphragms are positively moved upwardly and downwardly with small expenditure of power. I

The dominant object of this invention is to provide a flat-pulp screening machine, the diaphragm vibrating mechanism of which obviates the undesirable characteristics of the conventional diaphragm vibrating means,

without interfering with the recognized advantages and desirable characteristics of the conventional screen design and construction and diaphragm action. Supplementing the advantages afforded by the simplicity of design and the feasibility plate carrying members are flexibly and resiliently connected to the actuating means therefor. By virtue of this construction, the impacts of inertia forces resulting from perpendicular reciprocal displacement of the diaphragm plates at high velocities are substantially cushioned, resulting in reduction of bearing loads and knocks.

The invention is further characterized in that it affords a solution for the obvious desideratum of provision of diaphragm vibrating means adapted for application to the type of pulp screen in conventional use, without variation in the design of the pulp screen or extensive alteration in the structure in general.

Novel aspects, objects and advantages in addition to the foregoing may be ascertained by a perusal of the following description and from the accompanying drawing depicting one embodiment of my invention, and in which 2-- Fig. 1 is a longitudinal vertical sectional elevation of a pulp screen constructed in accordance with one selected form of my invention, the view being taken on'the plane represented by the line 1-1 on Fig. 2.

Fig. 2 is a transverse vertical section taken on the plane represented by the line 22 on Fig. 1, and

Fig. 3 is a horizontal section on the plane designated by the line 3-3 appearing on Fig. 2.

of adapting the presently disclosed form of Fig. 4 is a sectional detail showing the coupling between a rock shaft arm and a connecting rod.

Referring now to the drawing, 11 designates a plurality of perforated screen plates and 12 a plurality of flexible diaphragms disposed beneath the plates and suitably spaced therefrom. A wall 13 extending upwardly from the plates defines, with the plates, a trough or vat into which unscreened stock may be delivered. The plates and diaphragms are supported by a framework comprising upper and lower marginal members 14 and 15 and intermediate, members 16 and 17. The stock passes through the plates 11 into the space between them and the diaphragms, the passage of the stock being facilitated by vibration of the diaphragms 12 in the well known manner.

The framework together with the plates and diaphragms is'supported at its ends by the standards20, which are interconnected by the beam casting 21 carrying shaft bearings 22. The structure thus far described is standard and is the predominating form used in the industry. The mechanism for vibrating the diaphragms 12, which constitutes the present invention, will now be described.

According to this invention, a rock shaft 23 is journalled in the bearings 22. This shaft is preferably mounted substantially centrally beneath the diaphragms 12, extends longitudinally thereof, and carries a plurality of arms 24 which are arranged to project alternately from opposite sides of the shaft 23. 7 These arms may be keyed or otherwise suitably fixed to the said shaft, substantially vertically beneath the transverse centre lines of the diaphragms.

The diaphragms 12 may be secured between the diaphragm plates 25 and 26 in the usual manner known in the art. Connecting rods 27 are secured to the central bosses of the lower diaphragm'plates 26, are offset laterally and are partially in perpendicular alignment with the upwardly projecting shoulder pins 28 on the arms 24, and may in one form be secured thereto by means of sections of rubber hose 29 and clamps 30. A rubber cushion 31 may be placed beneath the lower end of each connecting rod 27 and the associated arm shoulder pin 28.

Th mechanism to rock the shaft 23 and oscillate the arms 24 may comprise the line shaft 32 carrying the eccentric 33 free to idle thereon and engageable by the claw clutch 34 splined to said line shaft. The eccentric rod 35 is pivoted as at 36 to the arm 37 keyed or otherwise suitably fixed to the shaft 23. The numeral 38 indicates one journal bearing of the said line shaft. The clutch control lever 39 and clutch engaging yoke may be of conventional design.

Screened stock leaves the machine through the usual passages, not shown, which communicate with the usualoutlet seal adapted v to maintain a suitable depth of stock over the In operation,'ro tation of the line' shaft 32 and the eccentric 33 when coupled thereto through the clutch 34 eflects actuation of the eccentric rod 35 and in turn oscillation of the arm 37, which effects partial rotation of the shaft 23 alternately in opposite directions. The rocking movement thus imparted to the said shaft effects oscillation of the arms 24 and reciprocal displacement of the connecting rods 27 and the diaphragm plates 25 and 26, resulting in vibration of the diaphragms It will be observed that, since the arms 24 project alternately on opposite sides of the shaft 23, upon rocking of the said shaft and oscillation of the said arms, alternate diaphragms are elevated while the intervening diaphragms are lowered, and vice versa upon reversal of the shaft rocking action, whereby a balanced effect is obtained which reduces strain to which the drive mechanism of the device is otherwise subjected.

Since the vibrating stroke of the diaphragms is short, the conventional practice being from to of an inch, upon oscillation of the arms 24 very little flexing of the resilient couplings 28 is effected, thus obviating the necessityof using hinge, or knuckle connections. Furthermore, by use of a flexible and resilient material, such as fabric reinforced rubber, each coupling serves as a shock absorber to dampen out the shocks resulting from perpendicular displacement of the diaphragms at high velocity.

It will be observed that the invention, as

herein disclosed, is particularly well adapted for application to machines which are now in use, without alterations in the screen plates 11 and the diaphragms 12, apart possibly from substitution of diaphragm plates 26 to enable properconnection of the connecting rods 27 thereto.

In the present invention, the total bearing surface of moving components. is reduced to the minimum and, due to the fact that "springs It will be understood that the invention is not confined to the details of construction disclosed in connection with the embodiment herein illustrated and described and that modifications may be substituted particularly in the manner of operating the rock shaft and in. the form of the oscillating arms and connecting rods and the manner of their connection to one another.

Having thus described my invention, what I claim is v 1. In a machine of the character described, in combination, a single row of diaphragms; a shaft journalled substantially centrally therebeneath disposed longitudinally with respect thereto; alternately arranged arms extending from opposite sides of said shaft; operative connections between said diaphragm and said arms; and means to rock said shaft and oscillate said arms.

2. In a machine of the character described, in combination, a single row of diaphragms; a shaft journalled substantially centrally therebeneath and disposed longitudinally with respect thereto; alternately arranged arms extending from opposite sides of said shaft; diaphragm plates; connecting rods fixed-at their upper ends to substantially the centres ofsaid diaphragm plates, and at their ower ends to the ends of said arms; and means to rock said shaft and oscillate said arms.

3. In a machine of the character described, the combination with diaphragms, of means for imparting vibratory movements to said diaphragms including a shaft; means, including flexible means, resiliently interconnecting said diaphragms and said shaft; and means to rock said shaft.

4. In a machine of the character described, the combination with diaphragms, of means for imparting vibratory movements to said diaphragms including a shaft means to partially rotate said shaft alternately in opposite directions; arms projecting laterally from said shaft; and flexible resilient operative connections between said arms and said diaphragms.

5. In a machine of the character described, in combination, a single row of diaphragms; a shaft journalled substantially centrally therebeneath disposed longitudinally with respect thereto; alternately arranged arms extending from opposite sides of said shaft; diaphragm plates; connecting rods fixed to said diaphragm plates and flexibly and resiliently connected to said arms; and means to rock said shaft and oscillate said arms.

6. In a pulp screening machine, a plurality of diaphragms arranged in a row; a shaft extending longitudinally of the row of diaphragms; arms fixed to and extending from said shaft alternately in opposite directions; operative connections between the arms and diaphragms, severally; and means to rock said shaft.

7. In a pulp screening machine, a plurality of diaphragms arranged in a row; a shaft extending longitudinally of the row of diaphragms; arms fixed to said shaft, one for each diaphragm and projecting alternately in opposite directions from the shaft; operative connections between said arms and said diaphragms, said connections each including a resilient element; and means to rock the shaft.

8. In apulp screening machine, a plurality of diaphragms arranged in a row; supporting plates associated with the diaphragms; a shaft extending longitudinally of said row of diaphragms; arms fixed to and extending alternately from opposite sides of said shaft;

connecting rods operatively connected to the diaphragm plates and to said arms, severally; and-means to rock said shaft.

In witness whereof, I have hereunto set my hand. i 1

JAMES R. DUNBAR. 

